Color Match Assets for 2D Animation
Since the color management applies at the very end of the chain, the sRGB transform curve modify the RGB values.
You will see a perfect match if you set the color management to linear (display device to none) save it as tiff with the checkbox save as render enabled, this way you can visualize a linear render without transformation.  

But remember for real light condition you need to set the display device to sRGB (if you have a sRGB monitor) otherwise you'll not see the light like in real life, due to all the transformation operating during the chain.
So depending of what you are doing exactly (you don't provide a lot of infos about your workflow) you need to choose the correct way of doing things depending if you want to display or work with your image and how you would mix different footages.

Here it's becoming a bit complex, remember real light intensity is linear, but the eyes apply a contrast curve (a bit like sRGB transform curve), so to see an image like we see the world with our eyes, we need to display a linear image with the monitor.  

The chain is like this:  


The render is linear  
We save it with a sRGB transform curve (not linear anymore)
The monitor transform it the opposit way, so the image is linear again
The eyes apply a contrast curve and we see it like really world


Light intensity is linear but we don't see it linear. It's a really interesting and hard topic to dive in.
Hope I have spread some light in.